VIVA Qs Flashcards
MRSA genes
mecA and mecC
Most common ESBLs
Escherichia coli (E. coli)
Klebsiella pneumoniae.
Pseudomonas aeruginosa.
Proteus mirabilis.
How would you investigate an ESBL
ESBLs are beta-lactamase producing so they are resistant to amoxicillin
Investigated by putting up ampicillin + amp+clav (augmentin)
What is augmentin?
Ampicillin + clavulanic acid
What is augmentin used for?
Treatment of ESBLs like E. Coli or Klebsiella
How would you confirm an ESBL?
Put up ampicillin + augementin
ESBL should be resistant to ampicillin
ESBL should be susceptible to augmentin as it contains clavulanic acid
How would you further investigate a confirmed ESBL?
A, B, C, D disc sensitivities to investigate if ESBL is AMPC producing
What are the 5 CPE genes
OXA48 (Dublin)
KPC (WEST)
NDM
VIM
IMP
CPE Molecular principle
Flow Flex PCR
BioFire Film Array PCR
Nested multiplex PCR
Roche Light Cycler PCR
Real Time PCR
Melting curve analysis
Gene Xpert PCR
Real-time PCR
MALDI-TOF
Matrix-assisted laser desorption/ionisation
Time-of-Flight
MALDI-TOF principle
Matrix added to sample
Sample is irradiated with a laser
ionised sample is separated accordinSg to mass in TOF tube
Pattern of fragments compared to database to ID organism
SediMax Principle
Uses bright-field and phase-contrast microscopy to visualise and recognise formed elements of urine
Enteric Genes (5)
C. diff = Toxin A and toxin B
Norovirus = G1 and G2
Campylobacter = tuf gene
Shigella = IpAH
Salmonella = SpaO
How to process a sputa
Label + book in
Describe appearance
Sputasol for 20 mins
Inoculate plates with 10ul sample
Dilution plate (10 in 20ml distilled water)
Disc blood + chocolate
How to process a BAL
Sputasol any mucoid samples for 20 min
Must be centrifuged
Pellet goes to TB
Supernatant used to inoculate plates
Separate loop for each plate
How to process a CSF
3+ samples
Alliqot for bio (glucose + protein)
Serial red cell count
White cell count on last sample
White cell diff if wbc >5
Film array (no gram)
Culture (if bacterial on blood and choc)
How to process a sample for TB
Any tissues must be mushed up and suspended in water
Sputa/Bals in sputasol for 20 mins
All samples spun for 20 mins
Auramine slide made
Sample spun down again + pour off supernatant
TB buffer solution added to pellet
Mixture used to inoculate TB bottles for BacT
How do you make an auramine O slide
Make slide with diamond tipped pen
Fix slides @ 70 degrees for 1 hour
Decontaminate slides (sputa/BALS/urines) with NaOH for 20 mins
Neutralise NaOH
Stain with Auramine O
When would you put up a geneXpert for TB?
If query atypical TB
- auramine slide is positive but BacT is negative
Most common organisms in BSIs
65% if BSI caused by E. Coli in MMUH (second most common worldwide)
Staphylococcus aures (first most common worldwide)
Strep pneumoniae
GNBs, ents and GPB e.g. diptheroids are also common
Rarely get yeast but they are a very serious infection
How long are blood cultures incubated
5 days for most
Query endocarditis = 7 days
Query Brucella = 21 days
What might cause a positive blood culture but negative subculture
High white blood cells
Overfilled bottle
Fastidious organism
What would you do with a positive blood culture but negative gram
Do a cytospin to condense any present bacteria down
What might cause a false negative BC?
S. pneumoniae auto-lysis
Most common causes of bacterial meningitis in adults
H. influenzae
S. pneumoniae
N. meningitidis
Most common cause of viral meningitis
70% enterovirus
Most common cause of meningitis in children
Adenovirus
MALDI principle
